-
Notifications
You must be signed in to change notification settings - Fork 0
/
sort.py
80 lines (63 loc) · 3.04 KB
/
sort.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
import heapq
import io
from math import sqrt
from serialization import content_length, go_to_pos, read_content, write_content
from util import tmp_file
# Assuming that `memory_size` values can be sorted in memory when memory_size values are also in memory.
# So approximately 3 * `memory_size` values fit into memory.
# It's also important that buffering stores float using 4 bytes for each one, while sorting operates on python floats,
# which are much fatter, but let's ignore it.
# P. S. It holds for each function
def merge_sort_stupid(fin: io.BufferedIOBase, fout: io.BufferedIOBase, memory_size: int, left=0, count=None):
fout.seek(0)
if count is None:
count = content_length(fin, preserve_pos=False)
if count <= memory_size:
go_to_pos(fin, left)
write_content(fout, sorted(read_content(fin, count=count)), batch_size=memory_size)
return
with tmp_file() as left_f, tmp_file() as right_f:
merge_sort_stupid(fin, left_f, memory_size, left, count=count // 2)
merge_sort_stupid(fin, right_f, memory_size, left + count // 2, count=count - count // 2)
left_f.seek(0)
right_f.seek(0)
write_content(fout, heapq.merge(read_content(left_f, batch_size=memory_size // 2),
read_content(right_f, batch_size=memory_size // 2)),
batch_size=memory_size)
def _to_sorted_blocks(fin: io.BufferedIOBase, memory_size):
while True:
sorted_values = sorted(read_content(fin, memory_size))
if not sorted_values:
break
f = tmp_file()
write_content(f, sorted_values)
f.close()
yield f
def _merge_blocks(tmp_files, fout: io.BufferedIOBase, memory_size: int):
# let's make output buffer slightly larger
# we can use 3 times `memory_size` for buffers
buffer_size = 3 * memory_size // (len(tmp_files) + 2)
for i, f in enumerate(tmp_files):
f = open(f.name, 'a+b')
f.seek(0)
tmp_files[i] = f
generators = [read_content(f, batch_size=buffer_size) for f in tmp_files]
write_content(fout, heapq.merge(*generators), batch_size=2 * buffer_size)
for f in tmp_files:
f.close()
# The same same is true about `memory_size` here
def merge_sort_k_blocks(fin: io.BufferedIOBase, fout: io.BufferedIOBase, memory_size: int):
_merge_blocks(list(_to_sorted_blocks(fin, memory_size)), fout, memory_size)
def merge_sort_k_blocks_two_passes(fin: io.BufferedIOBase, fout: io.BufferedIOBase, memory_size: int):
tmp_files = list(_to_sorted_blocks(fin, memory_size))
if len(tmp_files) < 10:
larger_tmp_files = tmp_files
else:
larger_tmp_files = []
larger_blocks_count = int(sqrt(len(tmp_files)))
for i in range(0, len(tmp_files), larger_blocks_count):
larger_f = tmp_file()
_merge_blocks(tmp_files[i:min(len(tmp_files), i + larger_blocks_count)], larger_f, memory_size)
larger_f.close()
larger_tmp_files.append(larger_f)
_merge_blocks(larger_tmp_files, fout, memory_size)